An epoxy resin is excellent in heat resistance, electric properties, dynamic properties, and the like and therefore widely used in the fields of various electrical and electronic parts, structural materials, adhesives, paints, and the like. Furthermore, in accordance with recent development of electrical and electronic fields, request for an epoxy resin has been higher, and particularly improvement of heat resistance has been required.
As a means for improving heat resistance of an epoxy resin, there are a method of improving structure of the epoxy resin itself by increasing functional group density in the epoxy resin to increase cross-link density of the cured product or by introducing a stiff skeleton into the resin skeleton, and a method of filling fillers such as glass fibers, silica particles, and mica. However, such a means by structure improvement of the epoxy resin itself or addition of fillers or the like has not attained sufficient improvement effects.
A heat resistance improvement method other than structure improvement of the epoxy resin itself or addition of fillers or the like is disclosed in, for example, JP-A 2001-59013 publication. Said publication proposes a method of using an alkoxy group-containing silane-modified epoxy resin which is obtained by subjecting a bisphenol A type epoxy resin and a hydrolyzable alkoxysilane to dealcoholization reaction. However, with regard to this method, there is pointed out a problem that defects such as voids tend to be caused in the cured product due to the alcohol and water produced as by-products.
Furthermore, as a compound having in the molecule silicon and an epoxy group similarly to said alkoxy group-containing silane-modified epoxy resin, JP-A 10-324749 publication proposes a polyorganosiloxane having an epoxy group and the preparation process thereof. However, this process necessitates a step of end-capping a hydroxyl group and/or an alkoxy group at the main chain terminals in order to improve stability. Moreover, in order to obtain the target product, the process necessitates multiple steps of introducing a mercapto group in advance and subjecting the group and an epoxy group-containing ethylenically unsaturated compound to Michel addition reaction in the presence of a radical initiator, and is not efficient. In addition, heat resistance of the resultant epoxy group-containing polyorganosiloxane is not referred to.